When Greta arrived in Athens, many people welcomed her holding Palestinian flags.
She said that serious things are happening in Gaza now, with many people injured and dying.
Greta told everyone that the focus should be on the people of Gaza, not on herself.
Recently, food and water in Gaza have been scarce, many people are sick, there are no medicines, and not enough doctors.
Many families have no safe place to live, and children are very hungry.
Greta said that helping others is not a crime, and we should care about the people of Gaza.
She hopes everyone will work together to make the world a better place.